Crossflow fans are known as air blowers as used in an indoor unit of a wall-mounted air conditioner. FIG. 22 shows one example of a crossflow fan. As shown in FIG. 22, a crossflow fan 104 is a type of fan through which air flow crosses transversely, and includes an impeller 141 formed by a number of blades 142. The blades 142 are forward-swept blades, in each of which the outer edge is located on the leading side from the inner edge with respect to the rotation direction Z1. When the impeller 141 is rotated in the rotation direction Z1 by an electric motor, cooled or heated air flow X (that is, conditioned air flow) in an indoor unit 1 of the air conditioner transversely passes through the impeller 141, in a plane perpendicular to the rotation axis Z of the impeller 141.
In the impeller of such a crossflow fan, air passing through the blades of the impeller generates noise. In an attempt to reduce such noise with a simple structure, crossflow fans have been proposed that have a plurality of notches formed at an edge of each blade (for example, see Patent Document 1). FIGS. 23 and 24 show a blade used in such a crossflow fan. As shown in FIGS. 23 and 24, a plurality of notches 242b are formed at an outer edge 242a of a plate-like blade 242. A basic shape section 242c is formed between each adjacent pair of the notches 242b. As shown in FIG. 25, the bottom 242y of each notch 242b extends in a direction substantially perpendicular to the sides of the blade 242. The blade thickness L6 in the vicinity of the bottom 242y of the notch 242b is equal to a blade thickness L5 of the basic shape section 242c. The notches 242b, which are formed in the blade 242 as described above, reduce trailing vortices (not shown) generated at an outlet region M of a crossflow fan 204. In other words, a simple modification to the shape of the blade 242 effectively reduces the noise of the crossflow fan 204.    Patent Document 1: Japanese Laid-Open Patent Publication No. 2006-125390